The atom is trying to achieve stability with 8 electrons in its outer shell. Basically it would like to look like its closest Noble gas. Metals tend to lose electrons to go back to the Noble gas configuration before it making the protons outnumber the electrons giving them a positive charge. Non-metals tend to gain electrons to look like the Noble gas ahead of them giving them a negative charge. So, 8 electrons in the outer shell is the goal.

To obtain a positive charge on the metal ion (which you have correct) doesn't the number of electrons DECREASE? by the number of + charges?
Na has 11p, 11 e.
Na^+ (+1 ion) has 11p, 10e
The + charge went up (from zero to +1), the number of electrons went down (from 11 to 10 = 1 = positive charge)